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United States Patent | 5,293,136 |
Ryat | March 8, 1994 |
A two-stage class-AB operational amplifier, that can be implemented either with bipolar or MOS transistors, includes a differential input circuit adapted to receive a differential input signal to produce an amplified differential output signal for application to first and second nodes. The differential input stage has a common-mode control circuit that produces first and second common-mode control voltages on the first and second nodes. The common-mode control voltages are combined with the amplified differential output signal on the first and second nodes to produce a first stage differential output signal. A high-swing output stage is connected to receive the first stage differential output signal. First and second current mirrors each have a mirror transistor to mirror an output current produced in response to the differential input signals on respective lines including the first and second nodes. The common-mode control circuit is in series with mirror transistors of the first and second current mirrors. A circuit clamps the first and second nodes at a voltage of 2V.sub.BE below the supply voltage, and clamps the voltage at the second node at a voltage of 2V.sub.BE above the reference potential, enabling the circuit to operate with improved power-supply rejection ratios.
Inventors: | Ryat; Marc H. (Santa Clara, CA) |
Assignee: | SGS-Thomson Microelectronics, Inc. (Carrollton, TX) |
Appl. No.: | 946764 |
Filed: | September 17, 1992 |
Current U.S. Class: | 330/258; 330/253; 330/255; 330/257 |
Intern'l Class: | H03F 003/45 |
Field of Search: | 330/252,253,255,257,258 |
4667165 | May., 1987 | De Weck | 330/258. |
4909953 | Feb., 1990 | McCormack | 330/258. |
5006817 | Apr., 1991 | Babanezhad | 330/258. |
5015966 | May., 1991 | McIntyre | 330/258. |
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